Characterization and immune role of class B scavenger receptor member 1 in spotted sea bass (Lateolabrax maculatus)

Scavenger receptors (SRs) are integral to the innate immune system and function as pattern-recognition receptors that facilitate pathogen clearance and mediate anti-inflammatory responses. However, the role of SRs in the immune response of Lateolabrax maculatus against Aeromonas veronii is unclear. Here, we cloned scavenger receptor B1 from L. maculatus (LmSRB1) and performed bioinformatics analysis to study its potential functions. The open reading frame spans 1530 base pairs and encodes a 509-amino acid protein with a molecular mass of 57.44 kDa. Comparative analysis revealed high sequence conservation among fish species. Expression profiling revealed strong LmSRB1 transcription in various tissues, especially in head kidney and spleen. Following A. veronii exposure, LmSRB1 expression initially increased, peaking after 4-8 h, with a notable secondary peak at 72 h. Fluorescence in situ hybridization indicated that LmSRB1 mainly localized to the cytoplasm, and subcellular-localization studies confirmed LmSRB1 protein expression in the cytoplasm and cell membrane. Enzyme-linked immunosorbent assay data showed dose-dependent binding of LmSRB1 to A. veronii. Modulating LmSRB1 expression significantly altered the levels of IL-8, IL-1β, TRAF6, and NIK. These results highlight the crucial role of LmSRB1 in L. maculatus's innate immune response to A. veronii and offer insights into improving the management of bacterial infections in aquaculture.